(591j) Dissolution of Semicrystalline Polymers: Solvent-Induced Decrystallization and Chain Untangling

A major barrier to the efficient utilization of biomass is the recalcitrance to dissolution of cellulose, presenting crystallinity and extensive noncovalent interactions (e.g., hydrogen bonding and hydrophobic).  Despite extensive research, the cellulose intra- and inter-molecular interactions and dissolution mechanism remain elusive.  In general, the dissolution of semicrystalline polymers such as cellulose comprises several steps including solvent penetration, decrystallization of crystalline domains, amorphous polymer swelling, and chain untangling.  The solvent-induced transformation of crystalline to amorphous domains and the polymer chain untangling are the rate-controlling steps in the dissolution of cellulose.  We quantify here the role of solvent in the cellulose decrystallization and chain untangling using a comprehensive phenomenological model describing the swelling and dissolution of solid semicrystalline polymer fibers.  In doing so, we present a clearer picture of the fundamentals of cellulose dissolution.  The insights obtained from this analysis facilitate the design of efficient solvent systems and conditions for biomass processing.